Windows Vista introduced the Windows Display Driver Model (WDDM), which allowed new features such as virtualized video memory and scheduling of concurrent graphics contexts. Windows 7 also uses WDDM, albeit a newer version. Microsoft had promised that Vista users wouldn't be left in the cold, and would be able to download and use DirectX 11. It included DirectX 11 in a beta version of its "Platform Update" available in September. The final version is now available via Windows Update. The Platform Update is meant for computers running Windows Server 2008 SP2 and Vista SP2, and is composed of four parts: The Windows Graphics, Imaging, and XPS Library contains DirectX 11, DirectCompute for hardware accelerated parallel computing, and the XPS Library for document printing.